1. Field of the Invention
The invention relates to a blown film extrusion installation for producing blown tubular plastic films.
2. Description of the Related Art
In blown film extrusion installations, a film tube is extruded from a round die, drawn off and thereby cooled and subsequently transformed from the round state into the laid-flat state by a lay-flat device. The lay-flat device may comprise fixed boards or co-rotating rollers or brush rollers. These laying-flat devices present no operational problems when the films being produced are of normal elasticity. However, when rigid films are produced and/or when there is low internal film pressure, folds may form which are difficult to eliminate because there are no suitable devices available for this. Spreading devices have been used inside the blown tubular film, but have not become widely adopted because they are too difficult to handle.